Fluid heat exchange apparatus



193%- R. SHELLENBERGER 2,054,954

FLUID HEAT EXCHANGE APP ARATUS Filed Feb. 2, 1934 2 Sheets-Sheet l INVENTOR Pa/f Shel/en b erger BY ATTORNEY Dec. 22, .1936. R SHELLENBERGER 2,064,954

FLUID HEAT EXCHANGE APPARATUS Filed Feb. 2, 1934 2 Sheets-Sheet 2 I ATTORNEY Patented Dec. 22, 1936 UNITED STATES PATENT OFFICE FLUID HEAT EXCHANGE APPARATUS Application February 2, 1934, Serial No. 709,400

4 Claims.

This invention relates to fluid heat exchange apparatus, and more particularly to that type of such apparatus which involves furnaces burning fuel in suspension and having water cooled 5 floors. Reference is here made to a slag tap type of furnace which involves heat resisting elements secured to fluid cooled tubes and interposed relative to those tubes and the burning fuel in the furnace to retain a pool of molten slag.

The molten slag collecting in furnaces of the type here considered has many of the properties of molten metal. It solidifies when suflicient heat units are extracted therefrom, and one of the factors determining the rapidity of its solidification is the size :or volume of the molten mass contacted by a heat absorbing body. It is a recognized physical phenomena that a thin stream of such molten material will solidify more quickly than a thick stream, other conditions remaining constant. solidification under either of these conditions depends upon the presence of material capable of absorbing sufficient B. t. 'u.s from the molten material. The temperature differential between such material and the molten mass will, of course, afiect the solidification or freezing. The rate of flow of the molten mass will also be a determining factor, this being a function of the viscosity of the mass.

Considering the various conditions above mentioned, there will be a rapid solidification or freezing of a molten mass if the mass or a part thereof is restricted to close confines; if the heat absorbing capacity of the confining body (or bodies) is great enough; and if the flow of the closely confined mass is not excessive. When the molten material is of excessive fluidity (or of low viscosity) either the degree of confinement, 40 or the heat absorbing capacity of the confining body, or both must be correspondingly high to accomplish a rapid freezing.

Applying the above principles to the construction of the floor of the present slag tap furnace, adjacent metallic floor elements are used as the bodies between which bodies of slag are confined. These elements are preferably positioned closely adjacent each other to make the confined slag bodies thin and to compensate for the high fluidity of the slag. They are secured in good thermal contact with water cooled floor tubes to give them a high heat absorbing capacity. Thus, a thin layer of molten slag passing from a slag pool into the spaces between adjacent elements will be subjected to contact with bodies which extract enough heat units to cause freezing.

Carrying forward this principle of the inven tion, the space between adjoining floor elements may have a continuation formed between the cooler (or outer) sides of the floor elements and the inner faces of bridge members or clamps which contact with the opposite sides of the cooling tubes. It is thus insured that the floor fissures or cracks will be of lengths sufficient to 0 cause the freezing of slag before it can emerge from the furnace.

Another practice in accord with the teachings of this invention involves the use of a plastic refractory in the joints between adjacent floor 5 elements. This material may be forced into the joints when the furnace is constructed. It subsequently contracts when it sets or vitrifies, thus producing the thin slag freezing cracks which prevent leakage from the slag pool in the bottom of the furnace.

Another procedure within the scope of the invention involves the use of slag flow retarding means placed in the floor cracks before the furnace is placed in operation. Thus, an incombustible and compressible material may be placed between the clamps and the floor elements at the ends of the above mentioned continuations of the slag freezing cracks.

Experience has shown that peculiar actions take place when some coals are burned in suspension in furnaces of the above indicated type. In such burning of coals having a high sulfur content, molten sulfides of iron are formed. Their properties, such as their extreme fluidity and corrosive qualities, make them difficult to control in the operation of furnaces of the type indicated. It has been found, for instance, that such molten sulfides cannot be successfully maintained as a part of a slag pool by furnace floors of types which are successful when other fuels are utilized. These molten sulfides, in prior art furnaces, will attack the floor elements and, because of their extreme fluidity, will flow through the joints between these elements and emerge from the furnace. Their erosive and corrosive qualities are such that they rapidly eat away the furnace floor elements and even the fluid cooled tubes, if a continued flow from the furnace takes place. This invention provides fluid cooled furnace floors which successfully overcome this difficulty.

The invention will be described with reference to the accompanying drawings, in which Fig. 1 is a detail sectional view illustrating the relationship of the floor blocks to the fiuid cooling tubes.

Fig. 2 is a partial plan view of the structure shown in Fig. 1 taken on the line 22 and looking in the direction of the arrows.

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 1.

Fig. 4 is a partial horizontal section of the complete furnace illustrated in Fig. 5, taken on the line 4-4 of that figure.

Fig. 5 is a view in the nature of a vertical section through a boiler and furnace installation embodying the present invention.

As indicated in Fig. 5 of the drawings, the walls of the furnace II] are delineated by rows of wall cooling tubes l2 and I4. Cooling tubes it also extend across the floor of the furnace. All of these tubes are preferably connected into the circulation of a steam boiler as illustrated. The tubes I! are shown to be connected to headers l8 and 20 which are in turn respectively connected to the steam and water spaces of the drum 22 by the uptake tubes 24 and downcomers 25. The tubes M are similarly connected to headers 28 and 30, the circulation of which is enhanced by the recirculators 32 and uptake connectors 34 discharging into the drum 22.

The floor tubes are connected at their discharge ends to a header 36 which communicates with the drum 22 through the tubes 38, the header 40 and the tubes 42. Water is supplied to the floor tubes through the downcomer tubes 44 which communicate with a header 46 joined with the inlet ends of the floor tubes.

The burner 48 is shown in position to discharge a slag forming fuel into the furnace between the tubes l4. The fuel preferably employed in the operation of these furnaces is pulverized coal which, when burned at high rates, produces a slag which is particularly destructive of refractory furnace walls. This destructive effect is particularly severe Where the fuel forms an ash which. may react with the refractory of the walls and flux it. The burning of some coals also results in the formation of molten iron sulfides which are difficult to maintain in a slag pool.

To prevent objectionable interruption of furnace operation due to the above indicated causes, the furnace floor, in this case, is formed by refractory metallic blocks 50 which are cooled by reason of thermal contact with the water cooled tubes above described. These blocks are preferably rectangular in form and are made of metal, filling the spaces between adjoining water tubes and pressed tightly against a substantial part of the circumference of each tube. They are short, as compared to the lengths of the tubes against which they are clamped, this arrangement being necessary to compensate for the differential expansion between the blocks and the tubes.

The blocks are clamped against the tubes as clearly illustrated in Fig. 1 of the drawings. Here, each block 60 has a connection at each end with a clamp or bridge member 52. Each bridge member is in the form of a casting having side portions 54 formed with tube engaging recesses as indicated Fig. 3. Each clamp 52 extends across the transverse joint 56 between two adjoining blocks, and is held in such spaced relation to the rear faces of the blocks that a slag solidifying passage 58 is formed therebetween. If any molten slag constituents flow into the joint 56 to the clamps 52 they will thereupon divide and flow in op osite directions recesses.

along the passages 58. This action not only involves the flow of molten slag in a thin layer between blocks and an adjacent clamp, but also the flow of slag along and in direct contact with the fluid cooled tubes. It is thereby solidified so that leakage from the slag pool in the bottom of the furnace is prevented.

As clearly indicated in Fig. 1, the clamps 52 are formed at their ends with recesses 60. Heat resisting material may be forced into these This serves to retard the flow and to thereby promote freezing of the slag. This invention also comprehends other circumstances in which slag flow retarding material is placed in the floor before the furnace is put into operation. When the joints or cracks between the floor elements are sufliciently large a plastic refractory material may be flushed into the joints orotherwise forced between those elements after they are assembled. When this material sets it contracts so as to leave crevices or joints of the desired thinness between the set material and floor elements. In this case, these cracks will be so thin that the heat absorbing capacity of the element promptly causes the freezing of any slag flowing into the crevices. Even when the cracks are made wider by the vitrification of the refractory material they are still so thin that their slag flow capacity when taken in conjunction with the heat absorbing capacity of the floor elements causes the quick freezing of slag which flows therein.

As indicated in the drawings, the clamps 521 are held against the tubes by studs 62, preferably screw threaded into the blocks and extended through openings in the clamps. Between the nuts 64 and the outer surface of the clamps are placed resilient members 66 which are put under pressure when the blocks and clamps are tightened against the tubes. These resilient members maintain tight contact between the tubes and the blocks in spite of differential temperature variations of the blocks, tubes and clamps over a wide range. Such variations would otherwise result in such differential expansion that good thermal contact between the blocks and the tubes would not be maintained.

The slag collects in a pool 68 indicated in Fig. 5 of the drawings, and it is periodically tapped through a slag tap opening when it has reached a certain level. After each tapping, the opening 10 is closed with refractory material and the operation of the furnace is again carried on until the slag has again reached tapping level.

In the particular boiler furnace installation shown in Fig. 5 of the drawings, the furnace gases proceed across the bank 12 of horizontally inclined steam generating tubes and then across the superheater 14 to the flue 16. The steam generating tubes are connected at their inlet ends to the water space of the drum 22 by the headers 18 and the downtake nipples 80 in the manner shown. At their outlet ends they are connected by uptake headers 82 and circulators 84 with the steam space of the drum 22. Tubular connections 86 conduct steam from the drum 22 to the inlet header 88 of the superheater, and superheated steam is conducted from the outlet header 9!! to a point of use.

While the invention has been described with reference to the particular combination of elements shown in the drawings, it is to be understood that it is not limited thereto, but that it is of a scope commensurate with the scope of the subjoined claims.

What is claimed is:

1. In a slag tap furnace construction for fluid heat exchange apparatus, spaced cooling tubes, separate metallic floor blocks secured to the tubes to form a furnace surface, and clamps spaced externally of the floor blocks and extending across the blocks to the tubesandforming therewith narrow slag solidifying passages communicating with the joints between the blocks transversely related to the tubes, said clamps covering the joints between the floor blocks and said blocks and tubes forming a construction adapted to maintain a pool of molten slag in the bottom of the furnace.

2. In a furnace construction for fluid heat exchange apparatus, spaced cooling tubes, separate metallic fioor blocks secured to the tubes to form a furnace surface, and metallic means spaced from and externally of the floor blocks and cooperating with the tubes to form narrow slag solidifying passages communicating with the joints between the said blocks, said means comprising clamp members each secured to adjacent floor blocks and bridging the joints between the blocks.

3. In a furnace construction for fluid heat exchange apparatus, spaced cooling tubes, separate metallic floor blocks secured to the tubes to present a furnace surface, and clamps extending across the joints between successive floor blocks and cooperating with the tubes to form narrow slag solidifying passages communicating with the joints between the floor blocks, the clamps also being spaced from the floor blocks.

4. A furnace construction comprising, in combination, spaced cooling tubes, means for maintaining fluid in the tubes, separate rectangular blocks secured to the tubes in alignment to form a furnace face, and block securing clamps bridging the joints between adjacent blocks, the clamps including parts spaced from the blocks to form passages leading past the transverse joints between adjacent blocks, and pressure members for securing each clamp to a plurality of blocks.

ROLFE SHELLENBERGER. 

